Mineral oil distillation



Feb. 1, 1938. l w. E. KUHN Er Al. 2,107,156

MINERAL OIL DISTILLATION Filed May 28 1934 Ped/.Iced

fr/face f/ ATTORNEY VPatented Feb. l, 193

UNlTED STATESl PATENT OFFICE 2,101,156 MINERAL on. msmLATIoN Wayne E. Kuhn and Lebbeus C. Kemp, Jr., PortA Arthur, Tex., assignors to The Texas Company, NewYork, N. Y., a corporation oi' Delaware Application my zo, 1934, serial No. 127,91 i' 'i Claims.

This inventidn relates to the distillation of hydrocarbon oils, and more particularly to the vacuum distillation of a topped crude oil to produce lubricating oil distillates and asphalt in a continuous process.

In co-pending application Serial No. 622,042, illed July l2, 1932, there is described the. distilla' tion of a topped crude oil by heating to a temperature below a normal cracking temperature,

separately heating a lighter kmore refractory oil, such as a gas oil or kerosene, to a materially higher temperature in excess of a normal craclring temperature, mixing the oils and simultane-y ing distillates are obtained. The present invention relates to improvements in the above described methods, and in apparatus for carrying out the improvements, whereby improved results and substantial economy in operation are effected. .Y In the U. S. patent to Coubrough No. 1,905,156, it has been suggested to separate lighter and r intermediate lubricant fractions from a reduced crude oil, thennmix a lighter oil such as a gas oil with the unvaporlzed residue, heat the mixture in a tube still to a temperature below crackfollowed, by flashing into a fractionating tower into which steam is introduced Vfor stripping the residuum, to obtain heavy lubricant fractions and asphalt as a residuum. In practice, it is found that substantial quantities ofrsteam arefrequ'ired in order to reduce the residuum to an 'asphalt of the proper-penetration.

It is an object ofthe present invention to provide a method of .distillation of. thischaracter,4

whereby lubricant fractions maybe substantially completely separated and asphalt of proper pene- -4 50 tration obtained as a residuum, -while enacting Y material economy in the consumption of steam,

andgto provide .simplified and economical ap-v fol'v this purpose.: A

The-invention contemplates .a method offdistilling a hydrocarbon oil, such as a topped crude oil, by heating the oil to an elevated temperature without cracking, dashing. into a dry vacuum fractionating zone where lighter and intermediate lubricant fractions are obtained together with a heavy unvaporized residue, separatelyv heating 5 a lighter'more refractory oil, such as a gas oil or kerosene, to ahigh temperatureat whichitwill ilash into vapor when introduced into a vacuum chamber, and ashing the unvaporized residue together with the heated lighter oil into 1u a separate vacuum fractionating zone, to which I' steam may be supplied to assist ixhehclistillation, and from which a heavy lubricant distillate fraction is separately obtained from the light oil distillate, and an asphaltic or tarry residue is removed as residuum.

The invention will be better understood in connection with the accompanying drawing which' is a diagrammatic view of a preferred embodiment of apparatus suitable for carrying out the.

process of the invention. I Referring to'tlie drawing, a pump VIii having a suction line Il and a discharge line i2 is arv ranged to deliver oil froma source (not shown) to a heating coil I3 situated in the upper portion 25 of a tubestill furnace f4. 'The oil is preferably 4 a reduced asphalt bearing crude, from which lighter constituents, including gasoline, kerosene and gas oil, may have been substantially removed inan atmospheric tube still distillation unit of conventional character. The oil is rapidly heated without any substantial cracking to a high temperature, for example about '150 to 800 F. or above, and then flashed by transfer-line I5 into l fractionating tower i6.

The fractionating tower It is divided by an impervious partition I8 into an upper dry vacuum sectionV IS and a lower wetvacuum section 20. While any suitable construction \of fractionating devices' may be employed, that shown, 40

consisting of a plurality of staggered downwardly inclined corrugated baiiies 2l, is found to function very satisfactorily, enabling a high vacuumv v Y tobe maintained throughout the tower while still obtainingradequate-fractionation and refluxing. Redux liquid is introduced by line 22. Certain of the .baiiles 2i are provided with liquid collecting sumps 22, from which lubricant side streams may be withdrawn throughthe valve controlled lines 2l, 25 and 2. Uncondensed vapors pass-over- 50 headbyline i'ltooneormorecoilcon 2 8, to whichxcooling medium is introduced by lines 29. condensate is removed from the con- 'densersbygravltylegstostoragetanks3L- Any lighter vapors and incondensable gasespass 5,

from the condensers through line 32y to a suitable jet or barometric condenser 33, or to a series of such jet condensers whereby'a'high vacuum equivalent to an absolute pressure of 25 to 50 mm. Hg. or less may be produced.

Unvaporized residuum, collecting in the bottom ofthe dry vacuum section i9 is passed through back-trapping line 35 controlled by -valve 36, which serves to introduce the residuum into the lower wet vacuum section 20 of the tower. A pump 31 withdraws a lighter more refractory oil, such as a gas oil or kerosene distillate, from tank 38 through suction line 39 and forces the oil throughpressure line to a heating coil 4I arranged in the lower hotter portion of furnace I4. The oil is here heated to a high temperature which is sufficient to reheat the'residuum to about the temperature at which it was introduced into the dry vacuum section, and which causes the lighter oil to iiash into vapor in the wet vacuum section to serve as a distilling medium. The highly heated lighter oil at a temperature of around 800 to 950 F. then passes by transfer line 42 into the back-trapping connection 35, where it is mixed with the unvaporized residue from the dry vacuum section of the tower, and the mixture having a temperature ofthe order of 750 to 810 F. or somewhat higher is flashed at an intermediate point in the wet vacuum section 20. Any suitable fractionating equipment may be provided for this section of the tower, such asthe inclined corrugated baflies'43 shown. A pipe con-` nection 55 is provided leading` into the upper portion of the chamber 20 for supplying a reflux or cooling medium thereto. Steam or an inert gas stripping medium may be introduced into the base of section 20 by line 44. One or more of viscous oil vaporized inthe wet vacuum section the bailles 43 may be provided withv a sump 45, from which a side stream of heavy lubricant distillate may be withdrawn by the valve controlled line 46. The arrangement is such that heavy 20 is substantially condensed therein and Withdrawn as a side stream, while the light distillate oil passes overhead by line' 48 to coil condenser 49, where it isicondensed and returned by gravity leg k5i) to tank 38. Any water, which may be condensed and accumulated in tank 38, is allowed to separate, and maybe Withdrawn through valve controlled discharge 5 I'. Uncondensed vapors and gases pass overhead froml condenser 49 by line 52 Vto a suitable jet or barometric condenser 53,

which serves to maintain a high vacuum equivalent to an absolue pressure of 25 to 50 mm. Hg. orv less on the section 20. With the larrangement shown, the absolute pressure may be readily carried and maintained as low'as 4 to 6 mm. Hg. Asphaltic residuum is withdrawn from .the base of section 20 by `valve controlled discharge 54.

By means of the present invention, the lighter and intermediate lubricant fractions, are. readily distilled and fractionally condensed under high vacuum, lwhich can be more effectively maintained due to the absence of steam. The heavy unvaporized residue, containing the heavy viscous lubricating oil fractions, which normally cannot be distilled without appreciable cracking, is then 1 directly mixed with the highly heated more refractory lighter oil, which imparts' additional heat to the residue and raises it to a high temperature. Due to the extremely short interval of time in which the oil is maintained at this high temperature, decomposition thereof is substantially prevented. The high vacuum, coupled with the vapor pressure eiiect of the Alighter oil,

, temperature.

as well as the vapor pressure eect of the stripping steam, enables a substantially complete separation ofthe viscous lubricating oils from the residue, with the result that a hard asphalt may be vdirectly obtained as residuum. Due to the fact that the gas oil or kerosene is not mixed with the bulk of the reduced crude, but only with the unvaporized residuefrom the dry vacuum section after the lighter and intermediate lubricating oils have been distilled off, a smaller proportion of the lighter oil may be employed. Consequently, the quantity of recirculating light oil is reduced, placing a decreased load on the `heater and condensing equipment. As the unvaporized residue from the dry vacuum section represents only a fraction of the volume of the originall reduced crude, the reduction in volume of lighter oil is'thereiore considerable. By separating the distillation of the lighter and intermediate lubricant fractions from the heavier lubricant fractions, and` by carrying out the former in a dry vacuum,,a smaller diameter tower may be employed, and less difficulty is experienced in maintaining a suitably highvacuum.

In certain cases, it may be feasible to dispense entirely with the use of steam in the lower section 20 of the tower. This vmay be accomplished by increasing the heat input by raising the temperature of the lighter oil, or by increasing the proportion of the lighter oil for a given Or, an inert stripping medium. such as a xed hydrocarbon gas, may be substituted for the steam. Avoidance of the use of steam possesses the advantage that the condensing and vacuum producing equipment is simpler and operates more eiliciently. `In any event, only relatively small quantities of steam are required to reduce theresiduum to an asphalt of suitable penetration, such for example as an A. S. T. M. penetration of from -1 to 4. For example, it has been found that,with the proportions and temperatures of the oils as set forth above, a quantity of steam varying from about 20 to 5 pounds or less per .barrel of reduced crude resulted in a reduction to an asphaltic bottoms representing about .4 to 6% weight on they weight wof the reduced crude.

While the invention is particularly suitable for the simultaneous production of distillate lubricating oils and asphalt in a continuous process, it may be Aused to advantage to distill residual or distillate oils toobtain lubricant distillate fractions and a heavy residuum or cylinder stock. For example, a heavy distillate oil or a reduced crude may be treated as above; or the oil may be heated to a temperature below a normal cracking temperature, such as below aboout '100 F., then flashed into the dry vacuum section where lighter `lubricant distillate fractions are obtained, the' residue is then ashedstogeth'er with a lighter oil,

which has been separately heated to a temperature materially above'a normal cracking temperature for the heavy oil, such as around 800 to 950 F., into the wet or second vacuum zone where distillation may or may not be aided withv steam, and where heavier lubricant distillate fractions are obtained together with an asphaltic residuum or heavy cylinder stock. In this manner, advantage is taken of high dashing temperatures, high vacuum, vapor pressure effect of the lighter oil, and short time of treatment at the high temperatures to secure viscous lubricant distillate oils while effectively avoiding 'any substantial cracking. A While the invention has been particularly described in connection with the employment of a dry vacuum in the upper fractionating section of the tower, it may be desirable in certain in stances to operate with the introduction of steam or an inert stripping medium in this section, and

a linej is shown for the purpose of introducing' such a medium. This may be employed with a somewhat lower vacuum in the tower, and any coolingeffectof the stripping steam or other medium may be compensated by the temperature and/or proportion of the lighter oil flashed with be. made without departing from the spirit and scope. thereof, and therefore-only vauch limitations should be imposed as are indicated in the appended claims. f

We claim:

1. The method of separating 1 cating oils and asphalt from a topped crude oil in a continuous process, which comprisesheating the topped crude oil to a distillation temperature while avoiding any substantial decomposition thereof and passing the oil into -a fractionating zone, fractionating the oil therein whilemaintainlng a substantial dry vacuum Vto produce 'distillate lubricating oil fractions and a heavy unvaporized fractiomwithdrawing the latter, separately heating a lighter more refractory oil to a temperature materially above the temperature of the withdrawn unvaporized fraction, simultaneously flashing the withdrawn unvaporized fraction and the lighter more refractoryoil into a Separate vacuum vfractionating zone in such manner that additional heat is imparted from thelighter more refractoryoil to the heavy fraction to thereby raise the temperature of the heavy fraction to a distillation temperature, b ut for such a'relaf tively short period of time that any substantial decomposition thereof is prevented, fractionating the mixturethereimwhile introducing steam into the separate fractionating zone to assist in the distillation thereinv to obtain a heavy distillate lubricating fraction,and removing an asphalt as residuum from the separate fractionatingY zone.

2. The method o f separating lubricating oils and asphalt from a topped crudeoil in a continuous process, which comprises heating the topped crude oil to a temperatureof around '150 to 800; F. while avoiding any substantial cracki ing thereof, passing the heated oil vinto a fractionating zone and fractionating therein while maintaining a substantial dry` vacuum to produce distillate lubricating oil fractions and a heavy unvaporized fraction, withdrawing the latter, separately heating a lighter more refractory 60 oil to a temperature materially abovethe tem-- perature of the withdrawn unvaporized fraction, mixing the heavy unvaporized fraction andthe lighter more refractory oil and ilashing the mixture into a separate vacuum fractionating zone jand fractionating therein while introducing steam into the separate fractionating zone to assist in the distillation and ttf-obtain a heavy' distillate lubricating fraction, and removing an asphalt as residuum from the separate fra'ctionating zone. Y I

3. The method of distilling a heavy hydrocarbon oil containing lubricant fractions, which comprises heatingithe heavy oil in a conned stream to a distillation temperature while avoiding any substantial cracking thereof and-nashing into a fractionating zone, fractionati'ng the oil therein while maintaining a substantial dry vacuum to produce distillate lubricating oil frac-` tions and a heavy unvaporized fraction, with-x drawing the latter, separately heating a lighter more refractory oil to a temperature materially above the temperature of the withdrawn heavy unvaporized fraction, mixing the withdrawn heavy fraction with the highly heated lighter oil, ashing the mixture into aseparate vacuum fractionating zone and fractionating therein to .separate a heavy lubricant distillate fraction from the lighter oil, stripping the residuum in the separate fractionating zone with steam, and

withdrawing the stripped residuum therefrom.

4. Vacuum distillation apparatus of the character described, comprising in combination, a fractionating tower having separate dry vacuum 4and wet vacuum fractionating sections, Aa tube -still flashing into the dry vacuum section, aI connection for back-trapping residuum from the dry vacuum section directly into the wet vacuum section, a separate heating coil discharging into the back-trapping connection, and means vfor passing anoil through the-separate-heating coil and thence' into. the back-trapping connection, from Where the mixture is ilashed into the wet vacuum section of the tower.

5. Vacuum distillation apparatus of the character described, comprising in combination, a fractionating tower having an upper vacuum fractionating section and alower vacuum fractionatingsection, the4 upper and lower sectionsl being closed from each other and having sep.-

f arate vapor withdrawals, a tube still flashing ,into the upper-vacuum section, a connection for fesV back-trapping residuum from the upper Vacuum section directly into the lower vacuum section,

- and a separate heating coil discharging. into the .ating zone. y

back-trapping connection, whereby a heated oil is mixed with the residuum and the mixture flashed into the lower vacuuxn section of the tower. T

6. The method of separating lubricating oils and asphalt from a topped crude oil in a continuous process, .which comprises heating the topped crude oil tol a temperature at which cracking would take place if the oil weremaintained at such temperature for any appreciable length of time, iiashing the'heated oil before anysubstantial cracking thereof occurs into a fractionating zone, fractionatihg the oil therein while maintaining a substantial dry vacuum to produce distillate lubricating oil fractions .and a heavy unvaporized fraction, withdrawing the latter, separately heating a lighter more refractory oil to a temperature materially above the stelri-l fractory oil to the heavy fraction to raisethe latter to adistillation temperature, but for such a relatively short period of vtime that any. sub-- stantial cracking thereof is prevented, fractionatingthe mixture therein while introducing steam into the separate Iracti'onatingA zone to assist in the distillation and to obtain a heavy distillate lubricating fraction, and removing anA asphalt as residuum from the separate'fraction- 7. Vacuum distillation .ilrst mentioned fractionating zone, additional heat being imparted from the lighter more re-v apparatus oi' vthe charu acter described, comprising in combination, a fractionating tower having an upper dry vacuum `section and a lower wet vacuul section closed from vapor communication -.with each other, separate vapor withdrawals from the said uppe dry vacuum section and the said lower wet vacuum section; separate vacuum producing means connected to the said vaporA withdrawals, a tube still ashing into the upper dry vacuum section, a

10 connection for back-tapping 'residuum from the upper dry vacuum section directly intothe lower wet vacuum section, a separate heating coil discharging into the back-trapping connection, whereby 'a heated ou is mixed with the residuum and the mixture ashed into the lowerwet vacuum section of the tower, and means for introducing steam into the lower wet vacuum section of the tower.

WAYNE E. KUHN.

LEBBEUS C. KEMP, Jn. 10 

